Stationary induction apparatus



Feb. 23 .1 926'. 1,574,640

' M. UNGER STATIONARY INDUCTION APPARATUS Filed May 26. 1921 2 Sheets-Sheet l Inventor: Ma. nus ungev,

His :ffttorney.

Feb. 23 .1926;

M. UNGER STATIONARY INDUCTIQNAPPARATUS Filed May 26, 1921 2 Sheets-Sheet 2 Inventor: a??? f 1 His flttovney.

Patented Feb. 23, 1926.

UNITE!) STATES PATENT OFFICE.

MAGNUS UNGER, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

STATIONARY INDUCTION AEPARATU'S.

Application filed May 26, 1921. Serial No. 472,879.

To all whom it may concern: Be it known that I, MAGNUS UNGER, a citizen of the United States, residing at Pittsfield, in the county. of Berkshire, State of Massachusetts, have invented certain new and useful Improvements in Stationary induction Apparatus.

My invention relates to stationary induction apparatus and has for its general object an improved economical, and readily manufactured arrangement of parts.

More particularly my invention relates to induction apparatus of the type applicable for use in connection with induction furnaces in which the charge constitutes the secondary of the transformer; a specific object being the provision of an arrangement which is rugged and is interlinkable with a furnace crucible.

In the induction type of electric furnace, it has generally been customary to employ an open and unprotected inducing winding in order to afford the air, which is generally the cooling medium employed, easy access to such winding. A winding of this construction is particularly disadvantageous in metallurgical work as it is exposed to fumes and dust which may impair or short circuit the turns of the winding. Also it may be wholly destroyed in the event of the crucible itself breakin The magnetic core too, in this type of furnace, has generally been constructed in a manner adapted for disassembly, since their removal from the crucible is often desirable; it being the practice to change crucibles whenever their useful life seems impaired, the heating, however, generally being ac complished always with the same induction apparatus. In the construction heretofore employed this disassembly could not be easily or quickly accomplished; a large number of core joints werein the path traversed by the magnetic flux; and altogether number of loose parts were involved, which did not make for efficiency either mechanically or electrically.

By my invention however these shortcomings are avoided, since I make use of a core composed of separable parts having substantially a minimum of magnetic joints, the same being secured together in a simple and rugged manner. Moreover, I employ a novel coil construction for the inducing winding which is insulated and protected against fumes, dust and possible breakage of the crucible. My construction, is particularly heat resistive and may be heated for long periods and to very high temperatures without in any manner impairing the con struction or insulation qualities of the windmg.

For a more complete understanding of the nature and objects of my invention ref erence should be made to the following detailed description taken in connection with the accompanying drawing in which:

Figs. 1 and 2 are views in perspective, showing first in disassembled and then in assembled positions, a core and inducing winding constructed in accordance with my invention. Fig. 3 is a diagrammatic view showing the induction apparatus of Figs. 1 and 2 applied to a crucible to make an in duction furnace; while Fig. 4 is a fragmentary detail view of a winding.

Referring now to the drawing, 10 denotes a U-shaped core member made of laminated magnetic material. This member cooperates with a T-shaped core member 11, also 'made of laminated magnetic material and has a winding 12 surrounding the leg 13. The T-shaped member is adapted to *fit on the upstanding legs of the U-shaped member to form a three-legged core as shown in Fig. 2; the T member being held to the -U member by means of clamping devices shown respectively at 1 1, 15 and 16.

A shell type core is thus formed of separable members, each of which comprises both a leg portion and a yoke portion. This is a particularly advantageous construction adapted for handling by cranes in furnace work, since by attaching the crane .to the yoke which is easily accessible, the winding which is usually less accessible may at the same time be moved.

Any convenient form of clamps at 14-, 15 and 16 may be employed, that shown comprises hook-shaped members 17 which an gage with recesses 18 formed in strips '19 laid along and secured to the legs o the core. These hook members have threaded shanks which pass through suitable holes in bars 20 which are drawn up against the core by nuts 21 which engage with the threaded shanks.

The arrangement shown yields a three legged core of the butt-joint type which. may be assembled and disassembled merely by manipulating the nuts 21. The core mem ber 11 with the winding 12 w iich is the inducing winding, when disassembled may be inserted readily in the annular breach of a crucible shown at 25 in Fig. 3, to maize an induction furnace; the core member 10 having been subsequently attaches.

The winding 12 is supported on the leg by the wedging action on insulating rods 2? and as previously indicated, is constructed in a rugged manner affording protection against fumes, dust, etc. To this end it is preferably wound edgewise from copper strap as a continuous helical spiral, as indi cated in Fig. l. The turns are insulated from each other by inserting segments of -mica or asbestos or each indiv'dual turn may n as be Wrapped with this material shown in Fig. 4:; other convenient nodes of applying it, however, may be employed. insulation is preferably covered with a refractory cement which will assist in holding the turns in place. The cement is inorganic,

heat resistant and electrically insulating.

For exam )le a caste formed b mixin ole; n 7 rc or nnely ground blast furnace inorgan c binder, such as silicate of sodium,

.1 sla with an may be used. The coil thus formed is now preferably given an exterior wrapping of asbestos tape which is filed with and covered with a refractory cement indicated at A coil of this construction is mechanically very strong and is well protected from the deleterious action of external agents. Such a coil ma be ooerated continuousl at a temperature of 500 C. for periods of time e2;-

ceeding in duration a wok without being impaired in any way.

As a final precaution, however, and in order to provide protection for the coil 12 against the molten metal which may escape in the event of the crucible breaking, it

. surround it with a metallic cyl nder 35 split and separated along some element as indicated at 86, such separation being employed to prevent short circuited current from flowing; the metal of this cylinder being preferably one of low 'magnetic permeability. The cylinder, fragments of which are shown in Figs. 2 and 4-, between the coil 12 and the surrounding furnace structures preferably supporting the crucible wall 37 so that the cooling air will pass between the winding and the metallic cylinder as indicated m F g.

The 'turn Having now described an embodiment of my invention which is at present the best means known to me for carrying the same into effect, I would have it understood that this is merely illust attire, and that I do not mean to be limited thereby to the precise details shown nor restricted in the choice of recognized equivalents except as defined in my claims hereunto annexed.

lV hat I claim as new and desire to secure by Letters Patent of the United States, is

1. Stationary induction apparatus for metal melting furnaces comprising a U shaped core member, a T shaped core memshaped core'member, a T shaped core mem-.

arranged to cooperate with said U shaped core member to form a threedcgged core, the middle of said core being the leg of said T shaped member, a primary winding surrounding said leg adapted to be inserted in the secondary loop of the crucibio of an electric induction furnace, a layer of heat refractory cementitious material applied directly to said winding so as to form a part thereof, said heat refractory material forming a continuous protective casing for the turns of said winding, and means for securing said winding to said le whereby said winding may be moved witfi said T shaped core member and thereby inserted in and removed from said secondary loop.

3. A winding for electrical induction furnaces comprising electrically conducting turns forming a coil, heat refractory electrically insulating material separating said turns, and a layer of heat refractory, electrically insulating cement applied to the exposes surfaces of said tn-ns so as to form a heat refractory electrically insulating coating enclosing said coil.

a. A winding for electrical induction fur naccs comprising electrically conducting turns forming a coil, layers of mica separating salt turns, and a layer of asbestos and heat refractory electrically insulating cement applied to the exposed surfaces of said turns forming a heat refractory elec trically insulating coating completely enclosing said coil.

5. A winding for electrical induction coating of heat refractory cement, and a layer of heat refractory electrically insulating cement covering and filling said tape.

In Witness whereof, I have hereunto set my hand this twenty-third day of May,

MAGNUS UNGER. 

